题解

#include <iostream>
#include <queue>
using namespace std;

using ll = long long;

queue<ll> q;

int main()
{
	ll n, c;
	cin >> n;
	
	while(n--)
	{
		cin >> c;
		switch (c)
		{
			case 1:
				ll t;
				cin >> t;
				q.push(t);
				break;
			case 2:
				if (q.size()) q.pop();
				else cout << "impossible!" << endl;
				break;
			case 3:
				if (q.size()) cout << q.front() << endl;
				else cout << "impossible!" << endl;
				break;
		}
	}
	
	return 0;
}